An unprecedented nitrogen elimination reaction: Mechanistic studies using N-15-labeled 4-amino-7-benzylpyrrolo[2,3-d][1,2,3]triazine-5-carbonitrile

[GRAPHICS] In the course of our work on novel pyrrolo[2,3-d][1,2,3]triazines we have d iscovered that 1 undergoes an elimination of nitrogen at 250 degrees C to g ive 2. We have conducted N-15 labeling studies that establish that the loss of N-2 and N-3 from 1 had occurred rather than N-1 and N-2, presumably via a retro Diels-Alder reaction of the imino tautomer 7. This study provides an alternative to the commonly accepted mechanism which involves the loss o f N-1 and N-2 via the transient formation of a diazonium compound generated from 4-amino- or 4-oxo-substituted 1,2,3-triazines condensed with carbocyc les or heterocycles.